Hepatitis C Virus (HCV) is one of the most prevalent causes of chronic liver disease in the United States, reportedly accounting for about 15 percent of acute viral hepatitis, 60 to 70 percent of chronic hepatitis, and up to 50 percent of cirrhosis, end-stage liver disease, and liver cancer. It has been estimated that almost 4 million Americans, or about 1.8 percent of the U.S. population, have antibodies to HCV (i.e., anti-HCV antibodies), indicating previous or ongoing infection with the virus. Hepatitis C causes an estimated 8,000 to 10,000 deaths annually in the United States. While the acute phase of HCV infection is usually associated with mild symptoms, some evidence suggests that only about 15% to 20% of infected people will clear HCV.
It has been reported that HCV is an enveloped, single-stranded RNA virus that contains a positive-stranded genome of about 9.6 kb. HCV is classified as a member of the Hepacivirus genus of the family Flaviviridae.
The HCV lifecycle includes entry into host cells; translation of the HCV genome, polyprotein processing, and replicase complex assembly; RNA replication, and virion assembly and release. Translation of the HCV RNA genome yields a more than 3000 amino acid long polyprotein that is processed by at least two cellular and two viral proteases. The HCV polyprotein is:NH2—C-E1-E2-p7-NS2-NS3-NS4A-NS4B—NS5A-NS5B—COOH.
The cellular signal peptidase and signal peptide peptidase have been reported to be responsible for cleavage of the N-terminal third of the polyprotein (C-E1-E2-p7) from the nonstructural proteins (NS2-NS3-NS4A-NS4B—NS5A-NS5B). The NS2-NS3 protease mediates a first cis cleavage at the NS2-NS3 site. The NS3-NS4A protease then mediates a second cis-cleavage at the NS3-NS4A junction. The NS3-NS4A complex then cleaves at 3 downstream sites to separate the remaining nonstructural proteins. Accurate processing of the polyprotein is asserted to be essential for forming an active HCV replicase complex.
Once the polyprotein has been cleaved, the replicase complex comprising at least the NS3-NS5B nonstructural proteins assembles. The replicase complex is cytoplasmic and membrane-associated. Major enzymatic activities in the replicase complex include serine protease activity and NTPase helicase activity in NS3, and RNA-dependent RNA polymerase activity of NS5B. In the RNA replication process, a complementary negative strand copy of the genomic RNA is produced. The negative strand copy is used as a template to synthesize additional positive strand genomic RNAs that may participate in translation, replication, packaging, or any combination thereof to produce progeny virus. Assembly of a functional replicase complex has been described as a component of the HCV replication mechanism. Provisional application docket no. A&P 18477.047, “Pharmaceutical compositions for and Methods of Inhibiting HCV Replication,” inventor Mingjun Huang, filed Apr. 11, 2005 is hereby incorporated by reference for in its entirety for its disclosure related to assembly of the replicase complex.
While previously known HCV inhibitors are suitable for their intended purposes, there nonetheless remains a need for additional HCV inhibitors. In addition, there remains a need for additional methods of treatment for HCV patients. Thus, there remains a need to develop, characterize and optimize molecules for the development of anti-hepatitis C drugs. Accordingly, it is an object of the present invention to provide such compounds, compositions and methods of treatment.